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Author Topic: AC line noise help.  (Read 7743 times)

Stephen Swaffer

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Re: AC line noise help.
« Reply #10 on: December 14, 2013, 01:33:09 am »

Also, keep in mind that if you decide to filter on the machine end, there is no reason to buy a filter big enough for everything.  It should be fairly simple to install a filter just ahead of the spindle drives.
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Mike Sokol

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Re: AC line noise help.
« Reply #11 on: December 15, 2013, 08:13:01 pm »

What I think is most interesting is that I can also hear the sound of (sounds like arcing) in the main transformer across the street when the machines break and to me that's crazy!
That arcing noise could be the hint. I've had a massive main transformer feeding a manufacturing plant lose a neutral connection internally. A lug had a loose bolt and created the problem. They said it was probably arcing and heating up for weeks, so we used an infrared camera to check all the other connections feeding the sub-panels. These was pretty big stuff with 600-amp 3-phase breakers feeding the sub-panels, and lots of damage happened from the open neutral.

It would be really interesting to have your journeyman electrician or power company pull the access panel from the big transformer and watch it at night while your machines break. However, be sure you use Arc Flash PPE gear (Personal Protective Equipment) since if a high current connection lets go while you're in blast zone, there will be an explosion of molten copper in a plasma hotter than the surface of the sun coming at you faster than the speed of sound. I've witness a few of those Arc Flash incidents, one up close and personal. And it's way more dangerous than simply being shocked.
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Jonathan Johnson

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Re: AC line noise help.
« Reply #12 on: December 16, 2013, 02:06:22 am »

I was in the panel that feeds the offices to see if there was any breaker space to pull two or three 20A circuits to an isolatioin transformer to see if we can get a handle on this. I had done nothing other than removed the cover and was summing up what was available when sparks shot out of the box! Upon inspection the neutral connection and buss were loose and arcing when the machines brake so we have some panel maintanance to do this weekend.

A good reminder to wear PPE (especially safety glasses) when opening electrical panels, even if you're not going to be working on them.

Even if the panel is dead, safety glasses are a good idea. You never know when something's going to let fly... a wire with spring pressure that releases unexpectedly... a bit of copper when you're snipping a wire... a bubble in the bottle of anti-corrosion goop that makes it splatter.
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Jerome Malsack

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Re: AC line noise help.
« Reply #13 on: December 18, 2013, 10:35:01 pm »

It might be worth looking at the computer network connecting to the milling if there is one and use fiber to connect the computer back to the main frames. 
also if possible us a fiber cable to connect the computer to the machine to prevent any transfer of the problem to the office level of power.   

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Tom Bourke

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Re: AC line noise help.
« Reply #14 on: December 19, 2013, 12:19:04 am »

That arcing noise could be the hint. I've had a massive main transformer feeding a manufacturing plant lose a neutral connection internally. A lug had a loose bolt and created the problem. They said it was probably arcing and heating up for weeks, so we used an infrared camera to check all the other connections feeding the sub-panels. These was pretty big stuff with 600-amp 3-phase breakers feeding the sub-panels, and lots of damage happened from the open neutral.

It would be really interesting to have your journeyman electrician or power company pull the access panel from the big transformer and watch it at night while your machines break. However, be sure you use Arc Flash PPE gear (Personal Protective Equipment) since if a high current connection lets go while you're in blast zone, there will be an explosion of molten copper in a plasma hotter than the surface of the sun coming at you faster than the speed of sound. I've witness a few of those Arc Flash incidents, one up close and personal. And it's way more dangerous than simply being shocked.
I also agree that you should have every panel and transformer inspected and re torqued.  One loose connection indicates there may be more.  Also those outdoor transformers are subjected to massive temperature swings out here.  Also another forum that may be able to help you is http://www.cnczone.com/forums/mazak_mitsubishi_mazatrol/  As far as I can tell that site is the prosoundweb of the machine world.
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Re: AC line noise help.
« Reply #14 on: December 19, 2013, 12:19:04 am »


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